GB903951A - Process for the manufacture of thiophenecarboxylic acids and their esters - Google Patents

Abstract

Compounds of the formula <FORM:0903951/IV (b)/1> where R1 is hydrogen or alkyl containing 1-4 carbon atoms, R2 is hydrogen, alkyl, aryl or acyl, R3 is alkyl, aryl or substituted aryl, or R2 and R3 together represent a tetramethylene chain, and R4 is hydrogen or alkyl containing 1-4 carbon atoms, are prepared by reacting the compound R1COCHR2COR3, or the acetal or a hydroxy- or alkoxymethylene derivative thereof, with thioglycolic acid or an ester thereof with an alkanol having 1-4 carbon atoms, to give a compound <FORM:0903951/IV (b)/2> or <FORM:0903951/IV (b)/3> esterifying with an alkanol having 1-4 carbon atoms if necessary, treating with an alkaline condensing agent such as an alkali metal hydroxide or alcoholate to effect ring closure, and if desired saponifying the thiophene carboxylic acid ester to the free acid. Specified dicarbonyl compounds or derivatives thereof are acetylacetone, butyrylacetone, valerylacetone, benzoylacetone, 3 - methyl acetylacetone, 3-ethyl acetylacetone, 3-butyl acetylacetone, 3-phenyl acetylacetone, a -acetyl propiophenone, a -butyryl butyrophenone, acetylacetaldehyde dimethylacetal, isovalerylacetaldehyde dimethylacetal, hydroxymethylene methyl ethyl ketone, hydroxymethylene diethyl ketone, 1-hydroxymethylene-cyclohexanone-(2), 3-hydroxymethylene heptanone-(4), hydroxymethylene propiophenone, hydroxymethylene - p - methyl - acetophenone, hydroxymethylene - p - methoxy - acetophenone, methoxymethylene acetophenone and ethoxymethylene acetylacetone. Examples prepare the following thiophene 2-carboxylic acids or esters: 3,4-dimethyl-, 3-ethyl-4-methyl-, 3:4-tetramethylene-, 3-phenyl-4-methyl-, 3-p-tolyl-, 3-p-anisyl-, 3-phenyl-, 3-methyl-, 3-isobutyl-, 3-methyl-4-acetyl-, 3,5-dimethyl-, 3,4,5-trimethyl- and 3-phenyl-5-methyl-.